SOLAR WATER HEATER
Based on the collector system, solar water heaters can be of two types.
Flat Plate Collectors (FPC) based Solar Water Heaters
The solar radiation is absorbed by Flat Plate Collectors which consist of an insulated outer metallic box covered on the top with glass sheet. Inside there are blackened metallic absorber (selectively coated) sheets with built in channels or riser tubes to carry water. The absorber absorbs the solar radiation and transfers the heat to the flowing water.
Evacuated Tube Collectors (ETC) based Solar Water Heaters
Evacuated Tube Collector is made of double layer borosilicate glass tubes evacuated for providing insulation. The outer wall of the inner tube is coated with selective absorbing material. This helps absorption of solar radiation and transfers the heat to the water which flows through the inner tube.
Solar water heating is now a mature technology. Wide spread utilization of solar water heaters can reduce a significant portion of the conventional energy being used for heating water in homes, factories and other commercial and institutional establishments. Internationally the market for solar water heaters has expanded significantly during the last decade.
Salient Features of Solar Water Heating System
Solar Hot Water System turns cold water into hot water with the help of sun’s rays.
Around 60 deg. – 80 deg. C temperature can be attained depending on solar radiation, weather conditions and solar collector system efficiency.
Hot water for homes, hostels, hotels, hospitals, restaurants, dairies, industries etc.
Can be installed on roof-tops, building terrace and open ground where there is no shading, south orientation of collectors and over-head tank above SWH system
SWH system generates hot water on clear sunny days (maximum), partially clouded (moderate) but not in rainy or heavy overcast day
Only soft and potable water can be used
Stainless Steel is used for small tanks whereas Mild Steel tanks with anti-corrosion coating inside are used for large tanks
Solar water heaters (SWHs) of 100-300 litres capacity are suited for domestic application.
Larger systems can be used in restaurants, guest houses, hotels, hospitals, industries etc.
Fuel Savings :
A 100 litres capacity SWH can replace an electric geyser for residential use and saves 1500 units of electricity annually.
Avoided uitility cost on generation:
The use of 1000 SWHs of 100 litres capacity each can contribute to a peak load shaving of 1 MW.
A SWH of 100 litres capacity can prevent emission of 1.5 tonnes of carbon- dioxide per year.
Life : 15-20 years
Approximate Cost : Rs.14000- 19,000 for a 100 litres capacity system and
Rs.110-150 per installed litre for higher capacity systems
Payback period : 3-4 years when electricity is replaced
4-5 years when furnace oil is replaced
5-6 years when coal is replaced